The subject matter of the present invention relates to detonators, and more particularly, to an exploding foil bubble activated (EFB) detonator for use in a perforating gun system, the bubble activated detonator including a polyimide layer adhesively secured to an exploding foil for expanding to form a bubble in response to a vaporization of a part of the foil, the bubble in the polyimide layer impacting a secondary explosive and detonating the explosive.
In the past, defense laboratories and related industries approached oil service companies to introduce a new detonator concept for use in perforating guns disposed in subsurface wells, an exploding foil initiator (EFI) detonator. The EFI detonator avoids the dangers associated with induced currents in primary highly sensitive explosives, the induced currents being produced when lead wires associated with arming apparatus in Electro Explosive Devices (EED) are exposed to electromagnetic fields originating from RF, radar, TV, and other electric transmissions. The EFI detonator is also termed the "flying plate" detonator, as illustrated in FIGS. 1, 2a, and 2b of the drawings and described in U.S. Pat. No. 4,788,913 to Stroud et al, entitled "Flying-Plate Detonator using a High Density High Explosive", the disclosure of which is incorporated by reference into this specification. The flying plate detonator includes a foil connected to a source of current, a small neck section of the foil exploding or vaporizing when a high current flows through the neck section of the foil. A disc is disposed in contact with the foil, the exploding neck section of the foil shearing a small flyer from the disc, the flyer travelling or flying through a barrel when sheared from the disc. The flyer impacts a secondary explosive and initiates a detonation of the secondary explosive. However, if the barrel is not centered correctly, an obstruction will appear between the disc and the secondary explosive. This obstruction will often prevent the flyer from impacting the secondary explosive. Therefore, when the flying plate EFI detonator is disposed in a perforating gun, this obstruction may prevent the perforating gun from detonating.